Diode string with reduced clamping voltage for efficient on-chip ESD protection

The standard steps of P- implantation and silicide block in the complementary metal-oxide semiconductor (CMOS) process are used in this design to implement the proposed diode string. The novel diode string realized by the diodes of P+ with N-well (P+/NW) and P- with N+ (P-/N+) is proposed in this letter. Besides, two diodes are merged together to form a silicon-controlled rectifier path to reduce the clamping voltage during electrostatic discharge (ESD) stress. The test devices of prior and proposed diode strings have been compared in a 0.18 μm CMOS process. With the higher current-handling ability and lower clamping voltage, the proposed diode string can be used as the efficient on-chip ESD protection device.